Conventionally, a toilet seat device for flushing a toilet stool may be provided with a human body sensor for sensing e.g. a user of the toilet stool. A commonly known example of the human body sensor is a photoelectric sensor.
However, installation of a photoelectric sensor requires providing a translucent window part in e.g. the surface or other location of the toilet seat device and embedding the photoelectric sensor so as to face the window part. Thus, the toilet seat device is defiled by the window part. Furthermore, a structure interrupting the light projection of the sensor cannot be provided in front of the window part of the photoelectric sensor. Moreover, the light projection part of the photoelectric sensor necessarily needs to be provided behind the window part. Such conditions cause the problem of e.g. limiting the flexibility of design of the toilet seat device, toilet stool, and other devices.
To solve this problem, there is proposed a human body sensing device using a Doppler sensor for human body sensing (e.g., Japanese Unexamined Patent Publication No. 2002-70119). Radio waves transmitted by the Doppler sensor can pass through e.g. resin. Thus, for instance, the Doppler sensor can be installed in the state of being hidden inside e.g. the toilet seat device. This can dispense with the window part required for the photoelectric sensor.
Furthermore, use of the Doppler sensor enables sensing the approaching motion of a human body and the leaving motion of a human body.
However, the human body sensing device using a Doppler sensor only determines the approaching motion of a human body and the leaving motion of a human body. It may fail to sense the presence of a human body when the human body comes to rest.
In particular, when a male user approaches a toilet stool to urinate, the user is in an almost stationary state during urination. Thus, the human body sensing device using a Doppler sensor causes the problem of malfunctions such as closing the toilet lid and flushing the toilet stool although being used by the user.
To solve this problem, there is known a toilet facility (toilet device) using a Doppler sensor with a plurality of amplifiers (e.g., Japanese Patent No. 4402406). When the toilet lid of the toilet stool is opened, the toilet facility switches the sensing sensitivity of the Doppler sensor to high sensitivity by switching to an amplifier of high gain and high sensitivity from among the plurality of amplifiers. This enables successfully sensing a human body even when the (male) user is in an almost stationary state for urination.
However, even if the sensitivity of the Doppler sensor is switched to high sensitivity as in the toilet facility of the aforementioned Japanese Patent No. 4402406, the state of little motion is difficult to sense and distinguish from the state of absence of a human body. Furthermore, because of the high sensitivity, the Doppler sensor is prone to generation of noise. This causes concern about malfunctions such as closing the toilet lid and flushing the toilet stool although being used by the user.
Furthermore, the need to use a plurality of amplifiers complicates the control circuit or sensor circuit. This also causes concern about increasing the load of the control section.
As a method to solve this problem, it is considered to determine that the user is present from the time of sensing the approaching motion of a human body until the time of sensing the leaving motion of a human body. However, for instance, the user may conduct a leaving motion directly after approaching the toilet facility without using it. In this case, there is concern about the occurrence of waste water caused by operations such as flushing the toilet stool although the toilet facility is not used.